British-born David Haines was killed by Islamic State (IS) a year ago whilst carrying out humanitarian work in Syria.
Writing in the Observer, his brother says since his loss he has "met many new people, from heads of state and religious leaders to community mentors."
On the day of David's death he is asking that all religious communities unite as one: "One simple gesture, one act, one moment - that brings people together."
He added that: "It is vital in ensuring our society is not broken apart by those wishing to cause us harm.
"My brother didn't see other nationalities or religions.
"He just saw human beings in need of help to get by or sometimes a lot of help to live another day."
Mike Haines met Pope Francis in May 2015 alongside Barbara Henning.
Henning was left a widow after Alan Henning, a volunteer in Syria, was beheaded by IS in 2013.
Mike Haines concluded saying: "I hope he is looking down and is proud of what can be achieved if we all stand together."
RIP David Haines pic.twitter.com/XS7YabgVxi
— Astonishing Pictures (@AstonishingPix) April 22, 2015